Performance based navigation

EGNOS

DSNA is implementing New Generation PBN Approach Procedures.
The progressive implementation of innovative satellite-based navigation technologies supports approach and landing operations without any specific airport-based infrastructure. DSNA is one of the shareholders of the ESSP-SAS (European Satellite Service Provider) company which provide EGNOS-based operations.

PBN baseline wording

PBN stands for Performance Based Navigation. GNSS (Global Navigation Satellite Systems), such as GPS, notably contribute to PBN requirements in both en route and terminal areas.

As part of DSNA PBN strategy and in particular for satellite based navigation, the following performance specifications have to be reached for each of the respective airspace areas :

Continental en route network : RNAV 5 specification
requires that the on-board equipment keeps lateral and longitudinal navigation accuracy on route of + 5 NM or better during at least 95% of the total flight time. It does not include requirements for on-board performance monitoring and alerting. The network based on the RNAV 5 specification (previously known as BRNAV in Europe) exists since 1998. To fly within the French airspace, RNAV 5 specification is required above FL 115.

Terminal area network : RNAV 1 specification
requires lateral and longitudinal navigation accuracy of +1 NM or better during at least 95% of the total flight time. On board performance monitoring and alerting are not required. RNAV 1 trajectories (previously known as PRNAV in Europe) are now implemented within more than 75% of DSNA terminal areas.

Three different types of approaches are supported by satellite systems. They are referred to as PBN approach procedures (published under the name RNAV(GNSS)) and require on board performance monitoring and alerting.

When monitoring and correction information of the PBN trajectory are needed, on board equipment will either use a Receiver Autonomous Integrity Monitoring (RAIM) or a Satellite Based Augmentation System (SBAS) such as EGNOS (European Geostationary Navigation Overlay Service) for Europe.

A SBAS increases the core GNSS constellation(s) by providing integrity, correction and GEO ranging information. Such systems are commonly composed of multiple ground stations, located at accurately-surveyed points.

Number of PBN approaches in DSNA area of responsibility

Breakdown by operating minima - March 2018 status

Implementation of PBN approaches was notably made possible through European co-financing programs : Trans-European Transport Network (TEN-T) and Connecting Europe Facility.

Aircraft capability is crucial to allow the spread of PBN and to maximize its benefits.

Additionally, RNAV 1 trajectories are now implemented within more than 75% of DSNA terminal areas.

What do YOU want to know about DSNA PBN strategy ?

Why publishing PBN/SBAS guidance (LPV MINIMA) ?

• DSNA wants to provide the best back-up solution in case of ILS failures or outages on its major airports. PBN/LPV procedures allow operating minima close to ILS CAT I.

The SBAS technology has proven to be as reliable and as performing as ILS CAT I operations and thus may complement ILS service at major airfields by providing identical operational minima and maintaining safe and optimum accessibility in case of unavailability.

The first implementation for Europe was at Paris CDG on April 28th 2016. Airlines and aircraft manufacturers have now the opportunity to clearly observe that PBN/LPV approaches support much higher airport accessibility than PBN approaches using other technologies. The operational benefits, in addition to the very high safety standards notably delivered by EGNOS, reinforce DSNA conviction that SBAS (System Based Augmentation System) is a key technology in modernizing its nav-aids infrastructure.

• DSNA deploys PBN approaches with LPV minima for all IFR runway ends, to make EGNOS benefits available to the entire aviation community ,and thus encourage retrofit.

Lateral & vertical guidance provided by a SBAS such as EGNOS is free of charge and has no airport infrastructure costs. SBAS fully support navigation and surveillance performance requirements.

PBN/LPV approaches based on SBAS are high performance/safety approaches. They have been highly appreciated by pilots during the various test campaigns that were carried out.

« As a test pilot, I had the opportunity to perform LPV approaches based on the EGNOS constellation on three different types of aircraft : A300ST, A350XWB and ATR72-600.The first observation, an unanimous one, is the ease of system acquisition because the pilot interface is designed like that of an ILS which is the best known and thus the most “intuitive” for use by an airline pilot. The second is that the LPV has better performance than even CAT I ILS because it is not sensitive to the “traditional” ILS disruptions, for example secondary LOC or Glide beams, or signal disruptions encountered when an aircraft overflies the localizer antenna. »
Jean-Christophe Lair - Airbus test pilot

• Today, PBN/LNAV-VNAV approaches based on delivered barometric information correspond to the most likely satellite navigation approach to be flown by airlines, but still suffer from some limitations :

QNH mis-setting events have been reported.
« RAIM unavailability » issues may occur when PBN is the unique existing approach.
As a reminder, Receiver Autonomous Integrity Monitoring (RAIM) is a technology developed to assess the integrity of the GPS signal in a GPS receiver system.

Anticipation is key to the evolution of PBN. DSNA will continue to deploy PBN/LPV minima approaches while maintaining the publication of GPS and Barometric guided procedures at runway ends of highest interest to its customers, hence taking into account the progression of the fleet equipment status.

What is DSNA’s position towards RNP 1 and radius to fix legs ?

One of the key concerns for DSNA in high density TMA is to guarantee optimal capacity at all times. With the introduction of RF (Radius to Fix) legs, capacity flaws may occur mainly due to additional radio exchanges and specific required ATC management in relation with unequipped aircraft. It is therefore difficult to introduce new functions, such as RF, without penalising the global TMA capacity, unless the equipment rate of aircraft operators approaches 100%.
One other means to derive benefits with RF would be to design specific trajectories to be flown during periods of low traffic only. This solution is under discussion with airspace users.

DSNA remains interested in future developments towards RF, but will need to monitor airlines’ equipment rates to support the future operational introduction of this function.

The transition from RNAV 1 to RNP 1 specification raises an issue that needs to be clarified : long term (say more than one day) loss of GNSS signal. With the RNAV 1 specification, a lot of flexibility for reversion is maintained, especially thanks to the large number of users equipped with DME/DME multimode receivers. However, interrogations remain regarding the acceptable conditions for using DME/DME along RNP 1 published routes when the outage lasts for a longer period. A meeting with Eurocontrol and EASA has been requested to clarify this issue and decide on the way forward.

It is DSNA intention to publish RNP 1 trajectories when it will be proven to be of operational relevance in terms of safety and performance. All projects and customers’ expectations in that regard will be looked into.

Will DSNA implement visual RNAV procedures ?

In close cooperation with Air France, DSNA designed and assessed a Visual RNAV approach at Bordeaux airport. Over 120 flights have tested it since summer 2015 with very positive feedback from both ATC and crews. The evaluation is still ongoing thus providing key inputs towards a new concept of operations to be defined at ICAO level and in the meantime gaining further practice for all first line actors.
Through a SESAR project at Nice airport, with participating partners, DSNA successfully designed and evaluated a visual RNAV approach in a very demanding terrain environment imposing a curved path until the short final.
A study has also started at Marseille airport, where obstacle-rich environment is also an issue and leads to the necessity of a steep slope to be followed by aircrews.

DSNA is ready to publish Visual RNAV approaches when the concept of operations will be agreed upon and established at ICAO level.

Looking into the future with GBAS CAT II/III ?

A Ground-Based Augmentation System (GBAS) is a system that supports augmentation of the primary GNSS constellation(s), at airport level, for all phases of approach : landing, departure and surface operations. While the main goal of GBAS is to provide integrity assurance, it also increases the accuracy of the signal.

HOP ! A commitment to PBN/LPV approaches

HOP ! is the new airline consolidating three French regional airlines of the Air France Group : Brit Air, Regional and Airlinair. HOP ! has a modern fleet of Embraers , Bombardier CRJs and ATR (12 ATR 42-500, 5 ATR 72-500 et 5 ATR 72-600) contributing to HOP ! Air France short haul activity : a vast network of 130 routes, mixing regional aircraft with Airbus 320 and 319 on the short haul point to point market. Each year, HOP ! carries over 1 000 000 passengers in 30 000 scheduled flights to 30 airports in France and Europe.

Alain Brothier, VP Fleet HOP ! Answers

PBN approaches with vertical guidance : improving safety on arrival

PBN@DSNA, an alternative to circling procedures and non-precision approaches

The extensive publication of PBN approach procedures with vertical guidance, with either LPV (Localizer performance with Vertical guidance) or LNAV/VNAV (Lateral NAVigation & Vertical NAVigation) minima on nearly all of DSNA runway ends provides aircraft operators with new accessibility possibilities, especially over a number of runway ends where precision approaches could not have been implemented leaving airport access pending on visual approach operating minima.

Runway ends for which non-precision approaches or circling/VPT (Visual pattern with Prescribed Track) are the only available procedures will see PBN approach with vertical guidance being published, until full coverage is achieved.

When weather conditions preclude the use of non-precision or circling approaches, or when confronted to ILS failures, PBN approaches with vertical guidance are reliable accessibility alternatives.

• CDG runway 08R, PBN with LPV CAT I or LNAV/VNAV minima published in 2016, as an efficient back-up solution in case of an ILS failure.

• MARSEILLE runway 31L, PBN with LPV or LNAV/VNAV minima, as an alternative to VPT

• GRENOBLE runway 27, PBN with LPV or LNAV minima, published in 2011, for a runway that used to be only accessible by following a circling approach.

• runway that used to be only accessible by following a circling approach.

In the particular case of runway 27 at Grenoble Isère (LFLS/GNB), even a PBN procedure with LNAV (Lateral NAVigation) minima improves accessibility as regards operating minima.

PBN approaches with vertical guidance reduce the risk of CFIT (Controlled Flight Into Terrain)

PBN approach - RNAV (GNSS) RWY 20 at Paris ORY

A striking example of additional safety benefits in a high density TMA

Moving from ILS to PBN

Since 2016, DSNA completed its ILS rationalisation plan. This plan was based on a simultaneous and ambitious deployment program of GNSS procedures for all IFR runway ends in France and overseas territories.

Indeed, satellite navigation technologies (GPS and EGNOS, the European satellite based augmentation system) make it possible to conduct landings without navigational aids on the ground, and at a lower cost (the signals being provided free of charge). To maintain the level of accessibility of small and medium sized airports, GNSS procedures have been implemented to replace the legacy ILS (Instrument Landing System). Nowadays, approaches following RNAV procedures and particularly Approach Procedures with Vertical guidance (APV) have shown performance close to ILS CAT I.

DSNA, the leading european provider in the implementation of satellite based procedures

There are two types of Approach Procedure with Vertical guidance, APV/SBAS (Satellite Based Augmentation System) and APV/Barometric Vertical NAVigation, which use different sensors to provide the vertical guidance during the approach. They are published on an approach chart entitled RNAV (GNSS) which can have several different minima lines, respectively LPV (Localiser Performance with Vertical guidance) & LNAV/VNAV minima (Lateral NAVigation & Vertical NAVigation).

PBN@CDG

Evaluation with real traffic of the concept “PBN to ILS” to implement round-the-clock CDO : since 18th January, 2021, around 350 flights at Paris-CDG airport incoming facing West on the North runway pair have operated on PBN satellite segments with accuracy in order to reach the ILS axis. All airlines are involved in this live trial. Read this leaflet to have a better understanding on the challenges of this innovative project !

April 2016 – PBN approach with LPV CAT I minima, a first for France

Starting by the southern runways, PBN approach procedures using a SBAS (Satellite Based Augmentation System) and allowing LPV CAT I minima have been in force at Paris CDG since April 28th, 2016. The north set of runways will see publication in the course of 2017.

• Simultaneously, PBN procedures with LNAV/VNAV minima have also been published for the southern set of runways to match the current equipment status of the fleet operating to Paris CDG.